package swust;
import java.util.Scanner;

public class ScoresOfLevel0035 {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		if(n < 60) {
			System.out.println("E");
		} else if (n < 70) {
			System.out.println("D");
		} else if (n < 80) {
			System.out.println("C");
		} else if (n < 90) {
			System.out.println("B");
		} else {
			System.out.println("A");
		}
	}
}
